It all started with the inventions of computers.
Initially, the computer didn’t come with a lot of storage space. The regular computers right now have a space of 500 gigabytes or 1 terabyte, but earlier on it was barely a few kilobytes.

To expand the storage, or store more files, floppy disks were utilised.
Just like how an external hard drive works for us, a floppy disk would help to store files which couldn’t be stored in the computer due to lack of space.

An external hard drive is merely an advanced version of the floppy disk.

To expand the storage, or store more files, floppy disks were utilized.
One could add both the floppies as a drive in the computer. Hence, the drives were named ‘A’ and ‘B.’

As the computers started advancing, the floppy drives went obsolete.
The computers started coming with a built-in hard drive so that more files could be stored.

With technological advancements, the floppy drives went out of the picture.
But the letters of the hard drives within the computer remained same.

Although, if one were so keen to organize the hard drives on the computer, it is possible.
You should be having administrative rights and a good knowledge of the workings of your computer in order to set the correct letters to your hard drives.